The objective of the research is to investigate the effects of prenatal exposure to marijuana upon the human infant at birth and through the first year of life. We will interview 950 women, participants in a prenatal obstetrics clinic in a public hospital, regarding their use of marijuana and other drugs during pregnancy. Their infants will be assessed at birth for the presence of minor physical anomalies, behavior variables and growth. The infants; health status, growth, motor and mental development will be re-evaluated when they are one year old. The research is designed to test the hypothesis, generated in a pilot study, that there is a dose-related reduction in birthweight associated with prenatal exposure to marijuana. It will also investigate teratogenicity as expressed in minor physical anomalies or subtle behavior variants. Use of marijuana by young women of child-bearing age is on the increase. At present, no information of the effects of prenatal exposure in the human is available. The proposed research will provide a basis for advising women about the consequences of marijuana use during pregnancy.